Comparison of infant and adult P300 from auditory stimuli.

Event-related brain potentials (ERPs) using auditory stimuli were recorded from 5- to 10-month-old infants and normal young adults with a passive tone sequence paradigm. A P3 (P300) component was obtained which demonstrated the same central-parietal maximum scalp distribution for both subject groups. P3 amplitude was smaller and its peak latency longer for infants compared to those of the adults across all electrode sites. P3 measures remained stable across stimulus trials indicating that ERP habituation was not occurring. Evaluation of individual subjects suggests that the P3 can be elicited from infants with auditory stimuli in a manner similar to that from adults and may serve as a useful index for the assessment of cognitive function in infants.     

Preliminary evidence for selective cortical responses to music in one-month-old infants

Prior studies have observed selective neural responses in the adult human auditory cortex to music and speech that cannot be explained by the differing lower-level acoustic properties of these stimuli. Does infant cortex exhibit similarly selective responses to music and speech shortly after birth? To answer this question, we attempted to collect functional magnetic resonance imaging (fMRI) data from 45 sleeping infants (2.0- to 11.9-weeks-old) while they listened to monophonic instrumental lullabies and infant-directed speech produced by a mother. To match acoustic variation between music and speech sounds we (1) recorded music from instruments that had a similar spectral range as female infant-directed speech, (2) used a novel excitation-matching algorithm to match the cochleagrams of music and speech stimuli, and (3) synthesized “model-matched” stimuli that were matched in spectrotemporal modulation statistics to (yet perceptually distinct from) music or speech. Of the 36 infants we collected usable data from, 19 had significant activations to sounds overall compared to scanner noise. From these infants, we observed a set of voxels in non-primary auditory cortex (NPAC) but not in Heschl's Gyrus that responded significantly more to music than to each of the other three stimulus types (but not significantly more strongly than to the background scanner noise). In contrast, our planned analyses did not reveal voxels in NPAC that responded more to speech than to model-matched speech, although other unplanned analyses did. These preliminary findings suggest that music selectivity arises within the first month of life. A video abstract of this article can be viewed at https://youtu.be/c8IGFvzxudk .

Research Highlights

• Responses to music, speech, and control sounds matched for the spectrotemporal modulation-statistics of each sound were measured from 2- to 11-week-old sleeping infants using fMRI.
• Auditory cortex was significantly activated by these stimuli in 19 out of 36 sleeping infants.
• Selective responses to music compared to the three other stimulus classes were found in non-primary auditory cortex but not in nearby Heschl's Gyrus.
• Selective responses to speech were not observed in planned analyses but were observed in unplanned, exploratory analyses.

     

Sensitivity to auditory‐tactile colocation in early infancy

An ability to detect the common location of multisensory stimulation is essential for us to perceive a coherent environment, to represent the interface between the body and the external world, and to act on sensory information. Regarding the tactile environment “at hand”, we need to represent somatosensory stimuli impinging on the skin surface in the same spatial reference frame as distal stimuli, such as those transduced by vision and audition. Across two experiments we investigated whether 6‐ (n = 14; Experiment 1) and 4‐month‐old (n = 14; Experiment 2) infants were sensitive to the colocation of tactile and auditory signals delivered to the hands. We recorded infants’ visual preferences for spatially congruent and incongruent auditory‐tactile events delivered to their hands. At 6 months, infants looked longer toward incongruent stimuli, whilst at 4 months infants looked longer toward congruent stimuli. Thus, even from 4 months of age, infants are sensitive to the colocation of simultaneously presented auditory and tactile stimuli. We conclude that 4‐ and 6‐month‐old infants can represent auditory and tactile stimuli in a common spatial frame of reference. We explain the age‐wise shift in infants’ preferences from congruent to incongruent in terms of an increased preference for novel crossmodal spatial relations based on the accumulation of experience. A comparison of looking preferences across the congruent and incongruent conditions with a unisensory control condition indicates that the ability to perceive auditory‐tactile colocation is based on a crossmodal rather than a supramodal spatial code by 6 months of age at least.     

Visual and auditory orienting responses in preterm infants: a comparison of three cohorts over time.

Visual and auditory orienting responses were compared in three cohorts of preterm infants (N = 351) born between 1977 and 1987. The infants were divided into one group born between 25 and 34 weeks gestational age (n = 140) and one group born between 35 and 37 weeks gestational age (n = 211). Ratings were made of the infants' best orienting responses to a bull's-eye, rattle, bell, voice, and face plus voice combined. Analyses of covariance were computed to adjust for changes in perinatal variables between 1977 and 1987. For both groups, there were significant differences between cohorts on orienting to the bull's-eye, with a trend for the 25- to 34-week group on orienting to the rattle. Behavioral outcome for preterm infants has improved with changes in neonatal intensive care.     

A PRELIMINARY PROCEDURE FOR PREDICTING THE POSITIVE AND NEGATIVE EFFECTS OF REINFORCEMENT-BASED PROCEDURES

In the current investigation, a modification was made to the preference assessment described by Pace, Ivancic, Edwards, Iwata, and Page (1985) to predict the effects of stimuli when used in a differential-reinforcement-of-other-behavior (DRO) schedule for 2 clients with severe self-injurious behavior (SIB) and profound mental retardation. Based on the results of the preference assessment, three types of stimuli were identified: (a) high-preference stimuli associated with high rates of SIB (HP/HS), (b) high-preference stimuli associated with relatively lower rates of SIB (HP/LS), and (c) low-preference stimuli associated with low rates of SIB (LP/LS). Consistent with the results of the preference assessment, the DRO schedule with HP/HS stimuli resulted in increased SIB, and the DRO schedule with LP/LS stimuli resulted in no changes in SIB. HP/LS stimuli were demonstrated reinforcers but did not result in a change in SIB when used in a DRO schedule. Thus, the stimulus preference assessment may be useful clinically in some situations for predicting both the beneficial and the negative side effects of stimuli in DRO procedures.     

Hemodynamic responses to speech and music in preverbal infants

Numerous studies have provided clues about the ontogeny of lateralization of auditory processing in humans, but most have employed specific subtypes of stimuli and/or have assessed responses in discrete temporal windows. The present study used near-infrared spectroscopy (NIRS) to establish changes in hemodynamic activity in the neocortex of preverbal infants (aged 4–11 months) while they were exposed to two distinct types of complex auditory stimuli (full sentences and musical phrases). Measurements were taken from bilateral temporal regions, including both anterior and posterior superior temporal gyri. When the infant sample was treated as a homogenous group, no significant effects emerged for stimulus type. However, when infants’ hemodynamic responses were categorized according to their overall changes in volume, two very clear neurophysiological patterns emerged. A high-responder group showed a pattern of early and increasing activation, primarily in the left hemisphere, similar to that observed in comparable studies with adults. In contrast, a low-responder group showed a pattern of gradual decreases in activation over time. Although age did track with responder type, no significant differences between these groups emerged for stimulus type, suggesting that the high- versus low-responder characterization generalizes across classes of auditory stimuli. These results highlight a new way to conceptualize the variable cortical blood flow patterns that are frequently observed across infants and stimuli, with hemodynamic response volumes potentially serving as an early indicator of developmental changes in auditory-processing sensitivity.     

Developmental changes in visual scanning of face and nonface patterns by infants

The eye movements of infants, aged 4–5, 7–8, and 10–11 weeks, were recorded while they viewed either a representation of a face or a nonface stimulus. Presentation of the visual stimulus was paired with the presentation of an auditory stimulus (either voice or tone) or silence. Attention to the visual stimulus was greater for the older two groups than for the youngest group. The effect of the addition of sound was to increase attention to the visual stimulus. In general, the face was looked at more than the nonface stimulus. The difference in visual attention between the face and the nonface stimulus did not appear to be based solely on the physical characteristics of the stimuli. A sharp increase in the amount of looking at the eyes of the face stimulus at 7–8 weeks of age seemed to be related to a developing appreciation of the meaning of the face as a pattern.     

Infant irritability and early mother–infant reciprocity patterns

This study investigated how various forms of neonatal irritability (at 3 days) and irritability at 10 weeks are related to reciprocal interactions between mothers and their infants. Fifty‐six fullterm, first‐born male infants were examined using the Neonatal Behavioral Assessment Scale (NBAS‐K) at 3 days postpartum. Each infant was rated for irritability to aversive stimuli, general irritability, consolability and responsiveness to visual–auditory stimuli. At 10 weeks of age, during a home visit, mother–infant reciprocity was scored for gaze, smile, vocalization and hold behaviors. Based upon maternal reports and behavioral observations, infant irritability was scored at 10 weeks using the NBAS‐K scoring system. Findings revealed that: (1) there were two distinct forms of reciprocity: social and physical; (2) general irritability at 3 days was negatively related to reciprocal hold interaction and positively related to reciprocal social interaction at 10 weeks, and (3) neonatal irritability to aversive stimuli (at 3 days) was positively related to subsequent reciprocal social interaction. Regression analyses showed that neonatal variables were the foremost predictors of reciprocal hold at 10 weeks. Findings are discussed in terms of (1) the need to differentiate between social and physical behavioral patterns, and (2) time‐lag effects with respect to mother–infant interactions. Copyright © 1999 John Wiley & Sons, Ltd.     

Electrophysiological responses to auditory novelty in temperamentally different 9‐month‐old infants

Behavioral reactivity to novel stimuli in the first half‐year of life has been identified as a key aspect of early temperament and a significant precursor of approach and withdrawal tendencies to novelty in later infancy and early childhood. The current study examines the neural signatures of reactivity to novel auditory stimuli in 9‐month‐old infants in relation to prior temperamental reactivity. On the basis of the assessment of behavioral reactivity scores at 4 months of age, infants were classified into groups of high negatively reactive and high positively reactive infants. Along with an unselected control group, these groups of temperamentally different infants were given a three‐stimulus auditory oddball task at 9 months of age which employed frequent standard and infrequent deviant tones as well as a set of complex novel sounds. In comparison to high positively reactive and control infants, high negatively reactive infants displayed increased amplitude of a positive slow wave in the ERP response to deviant tones compared to standard tones. In contrast, high positively reactive infants showed a larger novelty P3 to the complex novel sounds. Results are discussed in terms of optimal levels of novelty for temperamentally different infants.     

Hemispheric asymmetries in human infants: Spectral analysis of flash and click evoked potentials

Evoked potentials of 16 human infants (mean age = 5.0 weeks, SD = 1.8 weeks) were recorded from the left and right, occipital and temporal areas. Spectral analysis showed a high amplitude, localized, coherent center of activity within the left temporal area for click stimuli, and a high amplitude, localized center of activity in the right occipital area for flash stimuli. It was proposed that the structured auditory information of the click and the unstructured visual information of the flash represented different degrees of familiarity to the subjects. With this hypothesis, left hemisphere involvement in stimulus processing would increase as the stimulus became more referrable to previous long- or short-term experience. Conversely, right hemisphere involvement would increase with unfamiliar stimuli which could not be readily associated with earlier data.     

Intermodal enhancement of stimulus localisation in infants born prematurely

The interaction of auditory and visual modalities in the enhancement of orientation was examined in premature and near-term infants by presenting them auditory or visual stimuli or auditory-visual stimulus combinations at various positions in sensory space. In 4.5--15-mo-olds, brisk orienting responses could be elicited to very peripheral stimulus positions but only when the stimulus consisted of a spatially coherent auditory-visual combination (i.e., where a sound and a light occurred at the same point in space). This occurred for all infants, irrespective of age or gestational age at birth. First, the result shows that infants can respond to visual stimuli at eccentric positions, beyond the supposed limits of their effective visual fields as measured by standard perimetry. Second, the result extends earlier studies showing that intersensory integration and stimulus localisation develop relatively normally in prematurely born infants. The auditory-visual enhancement test as used here may have a number of further uses and applications in the clinic and laboratory.     

Developmental trends in auditory processing can provide early predictions of language acquisition in young infants

Auditory processing capabilities at the subcortical level have been hypothesized to impact an individual's development of both language and reading abilities. The present study examined whether auditory processing capabilities relate to language development in healthy 9‐month‐old infants. Participants were 71 infants (31 boys and 40 girls) with both Auditory Brainstem Response (ABR) and language assessments. At 6 weeks and/or 9 months of age, the infants underwent ABR testing using both a standard hearing screening protocol with 30 dB clicks and a second protocol using click pairs separated by 8, 16, and 64‐ms intervals presented at 80 dB. We evaluated the effects of interval duration on ABR latency and amplitude elicited by the second click. At 9 months, language development was assessed via parent report on the Chinese Communicative Development Inventory ‐ Putonghua version (CCDI‐P). Wave V latency z‐scores of the 64‐ms condition at 6 weeks showed strong direct relationships with Wave V latency in the same condition at 9 months. More importantly, shorter Wave V latencies at 9 months showed strong relationships with the CCDI‐P composite consisting of phrases understood, gestures, and words produced. Likewise, infants who had greater decreases in Wave V latencies from 6 weeks to 9 months had higher CCDI‐P composite scores. Females had higher language development scores and shorter Wave V latencies at both ages than males. Interestingly, when the ABR Wave V latencies at both ages were taken into account, the direct effects of gender on language disappeared. In conclusion, these results support the importance of low‐level auditory processing capabilities for early language acquisition in a population of typically developing young infants. Moreover, the auditory brainstem response in this paradigm shows promise as an electrophysiological marker to predict individual differences in language development in young children.     

Space aliens and nonwords: stimuli for investigating the learning of novel word-meaning pairs.

We describe a set of pictorial and auditory stimuli that we have developed for use in word learning tasks in which the participant learns pairings of novel auditory sound patterns (names) with pictorial depictions of novel objects (referents). The pictorial referents are drawings of "space aliens," consisting of images that are variants of 144 different aliens. The auditory names are possible nonwords of English; the stimulus set consists of over 2,500 nonword stimuli recorded in a single voice, with controlled onsets, varying from one to seven syllables in length. The pictorial and nonword stimuli can also serve as independent stimulus sets for purposes other than word learning. The full set of these stimuli may be downloaded from www.psychonomic.org/archive/.     

Contingent auditory feedback of arm movement facilitates reaching behavior in infancy

The purpose of this study was to investigate the influence of contingent auditory feedback on the development of infant reaching. Eleven full-term infants were observed biweekly from the age of 10 weeks to 16 weeks, and their arm kinematics were recorded. Auditory feedback that was contingent on arm kinematics was provided in the form of: (a) the mother's voice; and (b) musical tones. Results showed that providing auditory feedback (mother's voice or musical tones): (i) increased the amplitude of exploratory arm movements before the onset of reaching; and (ii) increased the number of reaches at the onset of reaching. These results show that infants are able to use contingent auditory feedback to explore the relevant possibilities for action that are subsequently shaped into goal-directed movements.     

Slow wave changes in amygdala to visual, auditory, and social stimuli following lesions of the inferior temporal cortex in squirrel monkey (Saimiri sciureus)

Radiotelemetry of slow wave activity of the amygdala was recorded under a variety of conditions. Power, and the percentage of power in the delta band, increased in response to stimulation. Recordings of monkey vocalizations and slides of ethologically relevant, natural objects produced a greater increase in power than did control stimuli. The responses to auditory stimuli increased when these stimuli were presented in an unrestrained, group setting, yet the responses to the vocalizations remained greater than those following control stimuli. Both the natural auditory and visual stimuli produced a reliable hierarchy with regard to the magnitude of response. Following lesions of inferior temporal cortex, these two hierarchies are disrupted, especially in the auditory domain. Further, these same stimuli, when presented after the lesion, produced a decrease, rather than an increase, in power. Nevertheless, the power recorded from the natural stimuli was still greater than that recorded from control stimuli in that the former produced less of a decrease in power, following the lesion, than did the latter. These data, in conjunction with a parallel report on evoked potentials in the amygdala, before and after cortical lesions, lead us to conclude that sensory information, particularly auditory, available to the amygdala, following the lesion, is substantially the same, and that it is the interpretation of this information, by the amygdala, which is altered by the cortical lesion.     

Electrophysiologic Manifestations of Impaired Temporal Lobe Auditory Processing in Verbal Auditory Agnosia

The present study examined the extent to which verbal auditory agnosia (VAA) is primarily a phonemic decoding disorder, as contrasted to a more global defect in acoustic processing. Subjects were six young adults who presented with VAA in childhood and who, at the time of testing, showed varying degrees of residual auditory discrimination impairment. They were compared to a group of young adults with normal language development matched for age and gender. Cortical event-related potentials (ERPs) were recorded to tones and to consonant-vowel stimuli presented in an "oddball" discrimination paradigm. In addition to cortical ERPs, auditory brainstem responses (ABRs) and middle latency responses (MLRs) were recorded. Cognitive and language assessments were obtained for the VAA subjects. ABRs and MLRs were normal. In comparison with the control group, the cortical ERPs of the VAA subjects showed a delay in the N1 component recorded over lateral temporal cortex both to tones and to speech sounds, despite an N1 of normal latency overlying the frontocentral region of the scalp. These electrophysiologic findings indicate a slowing of processing of both speech and nonspeech auditory stimuli and suggest that the locus of this abnormality is within the secondary auditory cortex in the lateral surface of the temporal lobes.     

Infant temperament and the brainstem auditory evoked response in later childhood.

Brainstem auditory evoked responses (BAERs) were evaluated on 10-12-year-old children (N = 56) who had been classified as high or low reactive to unfamiliar stimuli at 4 months of age. BAER measurement was selected because high reactive infants tend to become inhibited or fearful young children, and adult introverts have a faster latency to wave V of the BAER than do extroverts. Children previously classified as high reactive at 4 months had larger wave V components than did low reactive children, a finding that possibly suggests greater excitability in projections to the inferior colliculus. The fact that a fundamental feature of brainstem activity differentiated preadolescent children belonging to two early temperamental groups supports the value of gathering physiological data in temperament research.     

Stimulus novelty and cognitive-related ERP components of the infant brain

This study recorded visual fixation performance and event-related brain potentials (ERPs) to examine processing of novel visual information in 6- to 7-mo.-old infants as well as to test attention- or memory-related hypotheses of the functional significance of the Nc-ERP component. Separate groups of infants were presented two versions of a novelty-probe task with three types of visual stimuli: (a) a frequent face on 70% of the trials, (b) an oddball face on 15% of the trials, and (c) novel probe stimuli on the remaining 15% of the trials. The novelty probes were faces in one group and irregular shapes in the second group. Analysis showed longer fixations and Nc responses of greater amplitude occurred to oddball and novel stimuli. It was concluded that Nc reflects a top-down, controlled processing mechanism that flexibly allocates attentional resources.     

Comparison of Maternal Perceptions of Preterm and Fullterm Infants

We compared maternal attitudes and feelings in two groups of mother–infant dyads: 25 mothers with preterm newborns (M=30.9 weeks of gestational age) and 25 mothers with fullterm newborns (M=39.7 weeks of gestational age). Both groups were matched for infant sex, age (corrected in preterms) and birth order as well as for maternal age and education. Semi-structured interviews were used to collect data on maternal attitudes and feelings about pregnancy and the first contacts with the newborn. Mothers completed rating scales to indicate the specific behavioural problems they perceived in their infants at 6 weeks and 3 months of (corrected) age. Observations of infant responses to visual and/or auditory stimuli were made at 6 weeks and 3 months in a laboratory setting. At 3 months, each infant was administered the Bayley Scale of Mental Development. There were no differences in maternal attitudes and feelings between the two groups of mothers prior to the birth. However, significant differences appeared after birth and indicated increased anxiety in mothers of preterm infants. Significantly more 6-week-old preterm infants were perceived by their mothers as irritable and to cry more than fullterm infants. At the age of 3 months, both groups of infants differed only in terms of irritability. Differences between the two groups of mother–infant dyads, age-related changes in these differences and relationships between maternal evaluations and the laboratory-based assessments are discussed in the context of contrasts in the stability of behavioural regulation in preterm and fullterm infants.     

Effects of multimodal presentation and stimulus familiarity on auditory and visual processing

Two experiments examined the effects of multimodal presentation and stimulus familiarity on auditory and visual processing. In Experiment 1, 10-month-olds were habituated to either an auditory stimulus, a visual stimulus, or an auditory-visual multimodal stimulus. Processing time was assessed during the habituation phase, and discrimination of auditory and visual stimuli was assessed during a subsequent testing phase. In Experiment 2, the familiarity of the auditory or visual stimulus was systematically manipulated by prefamiliarizing infants to either the auditory or visual stimulus prior to the experiment proper. With the exception of the prefamiliarized auditory condition in Experiment 2, infants in the multimodal conditions failed to increase looking when the visual component changed at test. This finding is noteworthy given that infants discriminated the same visual stimuli when presented unimodally, and there was no evidence that multimodal presentation attenuated auditory processing. Possible factors underlying these effects are discussed.